Culvert Ambusher

The face-down spell has no mana cost and a mana value of 0. When you cast a face-down spell, put it on the stack face down so no other player knows what it is, and pay {3} to cast it. This is an alternative cost.

Any time you have priority, you may turn the face-down creature face up by revealing what its disguise cost is and paying that cost. This is a special action. It doesn't use the stack and can't be responded to. Only a face-down permanent can be turned face up this way; a face-down spell cannot.

Turning a permanent face up or face down doesn't change whether that permanent is tapped or untapped.

If the target creature is tapped or is affected by a spell or ability that says it can't block, then it doesn't block. If there's a cost associated with having that creature block, its controller isn't forced to pay that cost, so it doesn't have to block in that case either.

If a face-down creature loses its abilities, it can't be turned face up with a disguise ability because it will no longer have a disguise ability (or a disguise cost) once face up.

At any time, you can look at a face-down spell or permanent you control. You can't look at face-down permanents or spells you don't control unless an effect instructs or allows you to do so.